Nocardiosis is an acute or chronic, suppurative disease of humans caused by the soil-inhabiting aerobic mycelial organisms of the genus Nocardia. Although there are more than 40 species in the genus, only a very few are considered infectious and able to cause clinical disease in humans. The infectious species are generally deemed to include: N asteroides, N. brasiliensis, and N. caviae. There are three distinct clinical syndromes that may evolve from Nocardia infection: primary cutaneous; primary subcutaneous; and primary pulmonary and systemic. The primary cutaneous form of the disease occurs in persons following trauma and contact with soil. Cutaneous infection may present itself as cellulitis, pustules, pyoderma, or a lymphocutaneous form. The primary subcutaneous form of the disease conforms to the clinical entity known as actinomycotic mycetoma causing localized, deforming swollen lesions of suppurating abscesses, granulomata and draining sinuses. The primary pulmonary and systemic forms may be subclinical, pneumonic, chronic, or more rarely acute; the disease may become systemic by hematogenous spread. In this form, the infectious organism has a predilection for the central nervous system and, less commonly, other organs such as the kidney.
Infection with Nocardia species has become more common recently with the ever-increasing use of organ transplants and immunosuppressions associated with the treatment of many diseases [Simpson et al., Rev. Infect. Dis. 3:492-507 (1981)]. Clinical diagnosis normally requires the isolation of the causative organism from the subject's tissue or secretions. Unfortunately, this method of diagnosis is very time-consuming and often invasive procedures must be performed in order to secure adequate specimens for clinical evaluation. Some research studies have been attempted to develop a serological test for the diagnosis of nocardiosis; these studies have indicated that there exists a remarkable degree of immunological cross reactivity between tha Nocardia genus and other genera such as Mycobacterium [Kurup, V. P., Comp. Immunol. Microbiol. Infect. Dis. 2:69-74 (1979); Shainhouse et al., J. Clin. Microbiol. 8:516-519 (1978); Stevens et al., Am. J. Med. 71:928-934 (1981); Blumer and Kaufman, J. Clin. Microbiol. 10:308-312 (1979)]. Since nocardiosis is a potentially curable disease in humans, it is important that the physician make an accurate and timely diagnosis. Unfortunately, insofar as is presently known, there are no reliable and rapid methods available to meet this challenge. In addition, both epidemiological and clinical research investigations would benefit from the availability of more sensitive and specific methods for the detection of Nocardia based infections.